Compensating arrangement for thermal relays



May 4, 1943.

K. ASCHWANDEN 2,318,279 COMPENSATING ARRANGEMENT FOR THERMAL RELAYS Filed Nov. 27, 1940 [LUV/14770 I 7 o 7 f 2! Q /o 6 {Z WITNESSES: INVENTOR Patented May 4, 1943 COMPENSATING ARRANGEMENT FOR THERMAL RELAYS Karl Aschwanden, Berlin-Wittenau, Germany,

asslgnor to Westinghouse Electric & Manufacturlng Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 27, 1940, Serial No. 367,364 In Germany October 10, 1939 14 Claims. (01. 200116) This invention relates to circuit; interrupters and more particularly to compensating arrangements for the thermally responsive control device of the circuit interrupter.

One object of the invention is to provide a circuit interrupter having an improved thermal control device provided with an ambient compensating element and in which the operating thermal element does not have to overcome the rigidity of the compensating element in order to efiect operation of the interrupter.

Another object of the invention is the provision of a circuit interrupter having a thermally responsive control element and an improved ambient temperature compensating construction.

Another object of the invention is the provision of a circuit interrupter having a thermally responsive control element and an improved ambient temperature compensating means comprising an ambient temperature responsive bimetal element, the free end of which is resiliently connected to the thermally responsive control element.

Another object of the invention is the provision of a circuit breaker having an improved thermal control device having an ambient temperature compensating bimetal wherein the ther mal element and the compensating bimetal element are connected at their free ends and are given an initial tension, which is reduced or increased in response to changes in ambient temperatures.

Another object of the invention is the provision of a circuit breaker having an improved thermal trip device wherein an ambient responsive bimetal element varies the tension of a spring between the thermal element and the bimetal element to compensate for changes in ambient temperatures.

Another object of the invention is to provide a circuit breaker having an improved current responsive trip device wherein a trip member is disposed between a current responsive bimetal and an ambient responsive bimetal and springs are disposed between the trip member and the bimetal elements, the tension of the springs being controlled by the ambient responsive bimetal element to compensate for changes in ambient temperatures.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself,'however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in connection with the accompanying drawing, in which:

Figure 1 is a fragmentary elevational view, partly in section, showing a circuit breaker embodying the principles of the invention.

Fig. 2 is an end elevational view of the thermal trip device showing the compensating bimetal elements.

Fig. 3 is a plan View of the trip device shown inFig. 2.

Fig. 4 is a detail view showing a modification of the ambient compensating arrangement shown in Fig. 1.

Fig. 5 illustrates another modification of the trip device and the ambient compensating device.

Referring to Fig. 1 of the drawing, the circuit breaker illustrated comprises generally a base l 01 insulating material, a base plate 3, stationary contacts I! (only one being shown), a movable bridging contact IQ for cooperating with the stationary contacts I! to open and close the circuit, an operating mechanism indicated generally at 2| and a thermally responsive trip device indicated generally at 23.

The stationary contacts I! are mounted in the base- I in a suitable manner and the movable bridging contact I9 is mounted for reciprocal movement into and out of cooperative relation therewith. The bridging contact I9 is slidably mounted on a rod 25 projecting from a member 27 which is pivotally conneoted to the lower end of a switch lever 29 by\means of a pivot pin 3|. A coil spring 33 surrounding the rod 25 is compressed between the member 21 and the bridging contact and serves to provide contact pressure when the contacts are closed.

The operating mechanism 2! includes the switch lever 29 which is pivotally mounted on a pivot pin 35 supported in a main frame 3! comprising a pair of spaced side members 39 secured to the base plate 3. A latching lever 4| pivotally mounted on a pivot pin 43 supported on the frame 31 is operatively connected to the upper end of the switch lever by means of a toggle comprising toggle links 45 and 41. The toggle link 45 is pivotally connected to the lever 29 by a pivot pin 49 and the toggle link 41 is similarly connected to the latching lever M by a pivot pin 5|. The toggle links 45 and 41 are pivotally connected by a knee pin 53. The latching lever 4| is normally restrained in the position shown in Fig. 1 by means of a latch member 2 pivoted on a pivot pin it supported in the frame 31. The latch member 2 is adapted to be operated by the trip device 23 in response to overload currents to release the latching lever 4| to efiect automatic opening of the contacts.

A closing push button 55 is provided for manually closing the contacts. The push button 55 is mounted for sliding movement in the frame '31 by means of upper and lower guide plates 51 through the agency of the pin and slot con-- nections 53-6I, moves the knee of the toggle 45-41 downwardly through the dead center position wherein the knee pivot pin 53 lies below a line drawn through the pivot pins 49 and 5|. During the downward movement of the knee pin 53, the latching lever 4| is restrained by the latch member 2 in the position shown in Fig. 1. The downward movement of the knee of the toggle 45-41 consequently rotates the switch lever 29 counterclockwise, sliding the bridging contact l9 into engagement with the stationary contacts l1. When the contacts are closed, the force exerted by the spring 33 maintains the toggle 45-41 in its in toggle position against the influence of a spring (not shown).

but which biases the toggle overcenter in a direction to cause its collapse.

The circui' breaker, with the exception of the trip device 2'. is similar in construction to the circuit breal r fully disclosed in Patent No. 2,217,462, issued October 8, 1940, to H. H. Willmann and assigned to the assignee of the present invention.

The thermally responsive trip device which is provided to cause automatic opening of the circuit breaker in response to overload currents comprises a U-shaped bimetal element 5 secured to the base by means of screws 6 which pass through openings in mounting feet 4 formed on the lower ends of the legs of the bimetal element 5. The screws 6 also serve as terminals for supplying current to the bimetal element 5.

An adjusting screw 1, secured in the free end of the bimetal element 5 by means of a lock :-nut, is adapted, upon deflection of the bimetal element in response to overload currents, to en- -gage a projection '63 of the latch member 2 and rotate the latch membe counterclockwise (Fig. 1) to release the latchi g lever 4|. Upon release of the latching lever 4| the force of a circuit opening spring (not shown) rotates the switch lever 29 in a clockwise direction moving the toggle 45-41 toward the right, and rotating the lever 4| counterclockwise. During this movement of the toggle, the knee pin 53 slides toward the right in the slot 6| which is now in the low-er position. As soon as the force of the circuit opening spring is expended, the previously mentioned spring (not shown) causes the toggle 45-41 to move overcenter above the line 49-5l to its collapsed position, moving the push button 55 to its undepressed position and rotat' ing the tripping lever 4| to its Fig. 1 position. Following restoration of the latching lever 4|- to its normal position, a spring (not shown) rotates the latch member 2 clockwise to its latching position in which it reengages the latching lever 4|. The circuit breaker is now in the open position and the parts have been reset for the next closing operation.

Compensating means is provided to compensate for the influence of room temperatures on the current responsive bimetal element 5. The compensating means comprises a pair of bimetal elements 8 (Figs. 1 and 2) secured to the base plate 3 by welding or in any other suitable manner. The free end of each bimetal element 8 is provided with a clearance hole through which passes a screw 9. The heads ID of the screws cooperate with the bimetal elements 8 and the screws 9 are mounted in a transversely extending member H of insulating material which is rigidly secured to the free end of the bimetal element 5. Springs I2 are compressed between the compensating bimetal elements '8 and the ends of the member H and surround the shafts of the screws 9.

The bimetal element 5 flexes toward the left (Fig. 1) in response to overload currents to effect tripping of the breaker. As the room temperature rises, the bimetal elements 8 flex toward the right, increasing the tension of the springs |2, thus compensating for the influence of the rise in room temperature on the bimetal element 5.

According to the modification of the invention illustrated in Fig. 4, the springs |2 are replaced by the tension or spring force of the bimetal elements 8 and 5. This is effected by giving the bimetal elements an initial tension through the agency of the screws 9 so that they exert a tensile stress in opposite directions upon the screws. The screws 9 extend through the clearance openings in the free ends of the bimetal elements 8 and thread into the ends of the insulating bar I which is secured to the current responsive bimetal element 5. Thus the free ends of the bimetal elements 8 are connected to the free end of the bimetal element 5. Upon an increase in room temperature, the bimetal elements 8 tend to deflect in a direction toward the bimetal element 5, and the latter tends to deflect toward the bimetal elements 8 so that the stress exerted on the screw 9 diminishes without substantially changing the relative positions of the free ends of the bimetals 5 and 8. In this manner the influence of the room temperature on the positions of the bimetal elements is compensated for. By providing bimetal elements of different dimensions and characteristics, the positions of the bimetals may be varied by ambient temperatures so as to compensate for the influence of changes in room temperatures on the current responsive bimetal element.

Another modification of the trip device and the ambient temperature compensating feature is illustrated in Fig. 5. According to this modiflcation, a trip arm I 4 is pivotally mounted on a bracket l3 secured to the base of the breaker. The trip arm I 4 is disposed between a, current responsive bimetal element 5 and a bimetal element 8 which is responsive to ambient temperatures. Under normal conditions, the trip arm I4 is maintained in a central position between the bimetal elements by means of a pair of balanced springs l5, one of which is compressed between the trip arm and the bimetal 5, and the other of which is compressed between the trip arm and the bimetal 8.

The calibration of the bimetal elements 5 and 8 is such that they deflect an equal extent in opposite directions in response to fluctuations or room temperature, and cause equal compressions on expansion of the springs l5. Thus the trip arm H is maintained in its central position, even though the bimetal elements I and I deflect in response to room temperature changes.

When the bimetal element 5 is heated in response to overload currents, it deflects a greater amount and, acting through the right-hand one (Fig. 5) o! the springs i5, rotates the trip arm H in a counterclockwise direction. At this movement of the trip arm, a screw 1 mounted in the free end thereof engages the projection 53 and rocks the latch member 2 to effect release of the operating mechanism in the previously described manner. When the bimetal element 5 cools following an operation in response to an overload current, it resumes its normal position and the springs I5 again center the trip arm H.

In each of the embodiments of the invention the tripping point of the breaker may be readily adjusted by rotating the screw 1 to vary the distance of its operating end from the projection 63.

Adjustment oi the room temperature compensatlng device may be made by means of the screws 9 in the embodiments of the invention shown in Figs. 1 and 4. In the structure shown in Fig. 1, the screws 9 may be rotated to vary the initial tension of the springs I2. A similar adjustment may be made in the modification illustrated in Fig. 4 wherein the screws 9 serve to adjust the initial tension of the bimetal elements 5 and 8.

When the current responsive bimetal element 5 flexes in response to overload currents to effect trippin of the breaker, it is not required to overcome the rigidity of the compensating bimetal element 8, but only the relatively light force of the springs l2 in the Fig. 1 embodiment or the springs I5 in the modification shown in Fig. 5.

According to the compensating arrangement shown in Fig. 4, the current responsive bimetal element 5 is given an initial tension or deflection in tripping direction. The bimetal 5 must therefore be heated a predetermined amount according to the amount oi initial tension before it will displace its free end. Since this initial tension or deflection is in the tripping direction, it is obvious that the bimetal element 5 (Fig. 4) is not required to overcome any spring force, but only the light latch load in order to effect tripping of the breaker.

Having described several embodiments of the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made therein without departing from some of the essential features of the invention. It is, therefore, desired that the invention be interpreted as broadly as the prior art permits, and that it be limited only by what is expressly stated in the following claims.

What is claimed is:

1. In a circuit breaker, a trip device comprising a bimetal element operable in response to overload currents, a second bimetal element supported independently of said current responsive bimetal element, said bimetal elements being disposed to deflect in. opposite directions when heated, and a spring disposed between the free ends of said bimetal elements for applying a. force opposing tripping movement of said current responsive bimetal element, said second bimetal being operable in response to changes in ambient temperatures to vary the force applied by said spring to said current responsive bimetal element to thereby compensate for the influence of ambient temperatures on the current responsive bimetal element.

2. A trip device for a circuit breaker comprising a bimetal element rigidly mounted at one end and operable in response to overload currents, a second bimetal element rigidly mounted at one end and responsive to changes in ambient temperatures and disposed to cooperate with said current responsive bimetal to compensate said current responsive bimetal element for the influence of ambient temperatures, resilient means between the free end of said bimetal elements, and adjusting means on the free ends of said bimetal elements for adjusting the tension of said resilient means.

3. A circuit breaker comprising a bimetal element operable in response to overload currents, a second bimetal element cooperating with said thermally responsive bimetal element and operable in response to changes in room temperatures to compensate said thermally responsive bimetal for ambient temperature, adjusting means mounted on the free end of one of said bimetal elements and cooperating with the free end of the other bimetal element for adjusting the initial distance between the free ends of said bimetal elements, and means comprising a spring for biasing the free ends of said bimetal elements away from each other.

4. A trip device for a circuit breaker comprising a bimetal element operable in response to overload currents, a member movable with said current responsive bimetal element, a pair of bimetal elements each being responsive to changes in ambient temperature and disposed to cooperate with said member to compensate the current responsive bimetal element for the influence of ambient temperatures, resilient means disposed between the free ends of each element of said pair of bimetal elements and said member, and means for adjusting the initial tension of said resilient means.

5. A circuit breaker including a trip device comprising a bimetal element operable in response to overload currents. a second bimetal element responsive to changes in ambient temperatures, a trip member pivotally supported between said bimetal elements and operable by the current responsive bimetal element, and resilient means disposed between said trip member and each of the bimetal elements, said second bimetal element being operable in response to changes in ambient temperatures to vary the tension of said resilient means to thereby compensate the first named bimetal element for the influence of ambient temperatures.

6. A trip device for a circuit breaker comprising a current responsive bimetal element, a member supported on the free end of said bimetal element, a pair of bimetal elements disposed adlacent the ends of said member, means connecting each end of-the member to the pair of bimetal elements for giving all of the bimetal elements an initial tension, and means for adjusting said connecting means to vary the initial tension of said bimetal elements, said pair of bimetal elements being operable in response to changes in room temperature to vary the tension of the current responsive bimetal element to compensate the thermally responsive bimetal element for the influence of ambient temperatures.

7. In a circuit breaker including, a trip device comprising a bimetal element responsive to overload currents, a bimetal element responsive to ambient temperatures, said bimetal elements being independently mounted and disposed to defleet in opposite directions when heated, spring means intermediate the current responsive bimetal element and the ambient temperature responsive bimetal element, said ambient temperature responsive bimetal element acting in re sponse to changes in ambient temperatures to vary the tension of said spring, and adjusting means cooperating with the free ends of the bimetal elements for varying the tension of said spring.

8. In a circuit breaker including, a trip device comprising a current responsive bimetal element operable in response to predetermined circuit conditions, an ambient responsive bimetal element disposed to deflect toward the current responsive bimetal in response to an increase in ambient temperatures for compensating the current responsive bimetal for the influence of ambient temperatures, resilient means between the free ends of said bimetal elements for resiliently Opposing tripping action of the current responsive bimetal element, and adjusting means on the free ends of said bimetal elements for varying the initial tension of said resilient means.

9. In a circuit breaker, a trip device comprising a bimetal element operable in response to overload currents, a second bimetal element having an initial tension biasing the current responsive bimetal element in tripping direction, said second bimetal element being operable in response to changes in room temperature to vary the bias on the current responsive bimetal element to compensate the first named bimetal element for the influence of ambient temperatures, and means for adjusting the initial tension of said bimetal elements.

10. A trip device for a circuit breaker comprising a trip member, a bimetal element operable in response to overloads to operate said trip member, a second bimetal element having an initial tension biasing said current responsive bimetal element in tripping direction, said second bimetal element disposed adjacent the current responsive bimetal and operable in response to changes in room temperature to vary the bias on the current responsive bimetal element without changing the positions of the free ends of said bimetal elements relative to each other, and means intermediate the free ends of said bimetal elements for adjusting the initial tension of said bimetal elements.

11. In a circuit interrupter, a current respon sive bimetal element operable when heated a predetermined amount to cause operation of the interrupter, an ambient temperature compensating bimetal element having its free end associated with the free end of the current responsive bimetal element and operable in response to changes in ambient temperatures to produce a resilient force on said current responsive bimetal element to compensate said current responsive bimetal element for changes in ambient temperature, said current responsive bimetal element deflecting when heated by the current without overcoming the stiffness of the compensating bimetal element.

12. In a circuit interrupter, a current respon.

sive bimetal element operable when heated a predetermined amount to cause operation of the interrupter, an ambient temperature compensating bimetal element disposed adjacent said current responsive bimetal element, said elements being disposed to flex in opposite directions when heated, and means resiliently connecting the free ends of said bimetal elements to cause said compensating element to resiliently compensate the current responsive bimetal element for changes in ambient temperature.

13. In a circuit interrupter a current responsive bimetal element operable when heated a predetermined amount to cause operation of the interrupter, an ambient temperature compensating bimetal element cooperating with said current responsive bimetal element, said bimetal elements being disposed to deflect in opposite directions when heated, means connecting the free ends of said bimetal elements to cause said com pensating element to compensate the current responsive element for changes in ambient temperature, said connecting means permitting said current responsive element to operate when heated by current without bending said compensating bimetal element.

14.'In a circuit interrupter, a current responsive bimetal element operable when heated a predetermined amount to cause operation of the interrupter, a second bimetal element responsive to ambient temperature and disposed to cooperate with said current responsive bimetal element, said bimetal elements being disposed to deflect in opposite directions when heated, and means connecting the free ends of said bimetal elements to cause said ambient temperature responsive bimetal element to resiliently compensate the current responsive bimetal element for changes in ambient temperature, said connecting means permitting said current responsive bimetal element to operate when heated by the current without overcoming the stifiness of the ambient temperature responsive bimetal element.

KARL ASCHWANDEN. 

